//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19095 SUBJECT: IPN Triangulation of GRB 160225B DATE: 16/02/26 21:45:56 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, K. Hurley, on behalf of the IPN, V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, on behalf of the Fermi GBM team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report: The long-duration GRB 160225B has been detected by Fermi (GBM; trigger 478121069), Konus-Wind, INTEGRAL (SPI-ACS), Swift (BAT), so far, at about 69865 s UT (19:24:25). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary annulus centered at RA(2000)=174.671 deg (11h 38m 41s) Dec(2000)=+0.848 deg (+0d 50' 52"), whose radius is 43.602 +/- 8.004 deg (3 sigma). The minimum distance between the center line of this annulus and the MASTER-NET optical transient (Buckley, et al., GCN Circ. 19092 and 19094) is 19.5 arcmin, so the association of the OT and the GRB cannot be ruled out based on the triangulation only. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB160225_T69916/IPN/ The time history and spectrum will be given in forthcoming GCN Circulars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19096 SUBJECT: GRB 160225B: Fermi GBM detection DATE: 16/02/26 23:54:49 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC), E. Burns (UAH), and C. Meegan (UAH) reports on behalf of the Fermi GBM Team: At 19:24:25.39 UT on 25 February 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160225B (trigger 478121069 / 160225809) which was also triangulated by IPN (Svinkin et al., GCN 19095) The on-ground calculated location, using the GBM trigger data, is RA = 150.19 , DEC = -34.71 (J2000 degrees, equivalent to 10h 00m, -34d 42.0'), with an uncertainty of 1.00 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32]). The angle from the Fermi LAT boresight is 100 degrees. The GBM light curve shows two peaks with a duration (T90) of about 64 s (50-300 keV). The time-averaged spectrum from T0+43.009 s to T0+74.753 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.91 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 124.10 +/- 3.30 keV. The event fluence (10-1000 keV) in this time interval is (1.434 +/- 0.023)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+54.27 s in the 10-1000 keV band is 12.89 +/- 0.37 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog.